PCF8549 datasheet(18/36 Pages) PHILIPS

18 / 36 page

1997 Nov 21

Philips Semiconductors

Product speciﬁcation

× 102 pixels matrix LCD driver

PCF8549

Table 5

LCD bias voltage

Set VOP value:

The operation voltage VLCD can be set by software. The generated voltage is dependent of the temperature, the

programmed temperature coefficient (TC), and the programmed voltage at reference temperature (TCUT).

(1)

The voltage at reference temperature (VLCD(T=TCUT)) can be calculated as:

(2)

The parameters are explained in table 6.

The maximum voltage that can be generated is depending on the VDD2/2_HV Voltage and the display load current. The

relation ship is shown in Fig.16.

The charge pump is turned off if Vop[6 : 0] is set to zero.

For Mux 1 : 65 the optimum operation voltage of the liquid can be calculated as:

where Vth is the threshold voltage of the liquid crystal material used.

1012

1 : 24

1101

1 : 16

1110

1 : 9

SYMBOL

BIAS VOLTAGES

⁄

VLCD

(b-1)/b

× VLCD

(b-2)/b

× VLCD

2/b

× VLCD

1/b

× VLCD

VSS

BS[2]

BS[1]

BS[0]

b (RES. COUNT)

MUX RATE

LCD

VOP

⋅

()

CUT

–

() TC

⋅

LCD

aVOP

⋅

()

LCD

165

----------

–





⋅

--------------------------------------- V

6.85 V

⋅

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